1. Field of the Invention
The present invention relates to an image processing apparatus that has a function for forming images on both sides of a sheet, a control method therefor, and a storage medium storing control program therefor.
2. Description of the Related Art
An image forming apparatus is controlled so that an image forming operation and a sheet conveying operation are stopped when a paper jam (referred to as “a jam”, hereafter) occurs during conveyance of a recording sheet, and so that a subsequent operation does not start until a recording sheet on a conveyance path will be removed.
A plurality of recording sheets may stay on the conveyance path in the apparatus besides the recording sheet (jamming sheet) that is determined as a cause of jam at a jam occurrence point. The conveying operation and the image forming operation may be continued for a recording sheet that is nearer to an ejection port on the conveyance path (i.e., a downstream sheet) than the jamming sheet, and the downstream sheet can be ejected as-is.
However, conveyance of a recording sheet located in the upstream direction on the conveyance path from the jamming sheet stops like the jamming sheet.
A recording sheet (a residual sheet) that is remained on the conveyance path and is not a jamming sheet is likely not to be damaged unlike a jamming sheet. Accordingly, it is preferable to leave the residual sheet inside the apparatus and to re-convey the sheet after removing the jamming sheet to use without removing or discarding the residual sheet by a user.
Since such a use of a residual sheet saves user's time and trouble, and eliminates the need for discarding a recording sheet, it becomes a user's merit.
For example, Japanese Laid-Open Patent Publication (Kokai) No. H11-249506 (JP H11-249506) discloses an apparatus that does not remove a recording sheet located in the upper stream than a registration roller and that tries to use the recording sheet after a jam removal operation is finished.
However, since the conventional technique is premised on the case where an image is formed on one side of a recording sheet, it may not restart the image forming operation using a residual sheet when a jam occurs during an operation in a double-side mode that forms images on both sides of a recording sheet.
This is because an output product does not necessarily achieve a correct page order of recording sheets including a residual sheet when a recording sheet on which an image has been formed on a first side remains on a double-sided path as the residual sheet.
Timing of jam occurrence determines whether the residual sheet can be used or not. That is, there are two cases when the apparatus stops due to a jam and a residual sheet on which an image is formed on one side (front face) remains in a double-sided path. In one case, the residual sheet is able to be used after the jam is removed. In the other case, the residual sheet is not able to be used even after the jam is removed. This is a problem.